| With the development of science and technology,materials with special wetting properties such as waterproofing,anti-ice,anti-fouling,oil-water separation,and so on,have shown great potential applications and become current popular research.Cellulose,as a biodegradable natural material,has been widely used in various fields.The combination of superhydrophobic property and cellulose substrates can give theirs special property and the fiber antibacterial,breathable,flame retardant and other functions,which has research value and practical significance for improving the added value and functional development of the fiber.In recent years,some achievements have been made in the preparation and application of superhydrophobic cellulose fibers,but there are still many problems.The durability of superhydrophobic materials has become the main restricts in development.In addition,it is difficult for superhydrophobic fiber to realize large-scale and industrialized production owing to their complicated processes,expensive and un-green raw material.In order to solve the above problems,a stable micro/nano structure was constructed on the surface of cotton fiber by chemical etching with sodium hydroxide/urea system,and the formation mechanism of micro/nano structure was analyzed.Using etched fiber as substrate,durable superhydrophobic fiber was prepared by designing the combination mode of intermediate medium and hydrophobic compound with fiber substrate,and the influence of micro/nano structure and low surface energy compound with different weting characteristics on the construction and performance of durable superhydrophobic surface was revealed.In addition,the flame retardant nano-sodium hydroxide coating was applied to the etched fiber to prepare the flame retardant superhydrophobic fiber,and its application in oil-water separation was analyzed.The main work and results are shown as follows:The stable surface with micro/nano structure of the fiber was constructed by chemical etching of the fiber with NaOH and urea at low temperature.The influence of etching conditions on morphology was investigated.It was found that by adjusting NaOH concentration,stable grooves or "worm bite" morphology of micro-nano structure surface could be obtained,and it was proposed that the formation of "worm bite"surface structure was due to the effect of micro-dissolved fiber deposition.The microstructure of the fibers before and after etching was characterized by atomic force microscope(AFM),fourier infrared spectroscopy(FTIR)and X-ray diffraction(XRD).The results showed that the roughness of the fibers increased and the crystallinity decreased after etching.Compared with conventional chemical etching,sodium hydroxide/urea etching improved the mechanical properties of cotton fabrics.These changes were more favorable to modify fibers with hydrophobic compounds.Using etched fiber as matrix materil,the superhydrophobic fiber was prepared by modifiers of hexadecyl trimethoxysilane(HDTMS)and butane tetracarboxylic acid(BTCA).The effects of etching conditions and hydrophobic content on the morphology and wettability of superhydrophobic surface were investigated by using SEM and contact angle measuring instrument(OCA).The durability of superhydrophobic fabric was analyzed by friction and washing,impregnation with acid-base solution and hot drop test.The results showed that the rolling Angle of the surface topography of the grooves or gaps was about 35°?60°,and the viscosity of the droplets on the insect-bitten surface remained the same even if the droplet was turned 180°.As a crosslinking agent,BTCA can effectively improve the friction property and washing property of superhydrophobic fiber surface and acid and alkali resistance,but it damages the mechanical strength of the fiber.The long chain hydrophobic monomer was introduced into acrylate emulsion with good film forming performance to construct superhydrophobic cotton fiber coating.The synthesis process,wettability,durability and physical properties of the superhydrophobic coating were discussed.The studies showed that when mSMA/mBA was 18,mCTAB/mAEO-20 was 1/2 and contentration of emulsifi was 6%,HEA was 1.5%,and DMC was 1.2%,the synthesized emulsion possessed good stability and uniform dispersion with a particle size of about 200 nm.The performance of POA was analyzed by FTIR,SEM,transmission electron microscope(TEM)and thermogravimetric analyzer(TGA).When the dosage of POA was 100 g/L,the contact angle of the coated fiber was 154° and spray rating could reach 90.As a superhydrophobic fiber for textile,POA coating not only maintained the surface morphology of the fiber,but also had good air permeability and moisture permeability.However,the superhydrophobic fiber showed poor friction and washing resistance.Based on the consideration of durability,a blocked waterborne polyurethane(WPU)crosslinking agent was synthesized.The effects of R value and MDEA on the emulsion properties and film properties of WPU were analyzed.The results displayed that when the R value was 1.7 and MDEA was 5%,the emulsion had the best performance and the water absorption rate of the film was lower.The structure,morphology and thermal stability of WPU emulsion were investigated by means of FTIR,SEM and TGA.Under high temperature baking,WPU released active group-NCO,which could combine the hydrophobic compounds(POA)and substrate layer tightly by covalent crosslinking.When the optimum content of WPU was 20%,the contact angle of superhydrophobic fiber reached 155°,the water absorption is 6%,and the friction resistance counld reach 4000 times.The flame retardant superhydrophobic fabrics was prepared by using Mg(OH)2 nanoparticles with flame retardant properties and polydimethylsiloxane(PDMS)modified fabric with high adhesion.The effects of Mg(OH)2 content on the surface hydrophobic properties and microstructure of the original and etched fabrics were compared in detail.The friction resistance,washing resistance,acid and alkali resistance and solvent resistance of the superhydrophobic coatings were investigated.The results show that,compared with the original fabric,the etched fabric has a higher load of Mg(OH)2 and a larger contact angle.At the same time,the friction resistance and washing resistance of the superhydrophobic coating are significantly improved.The flame retardant performance was analyzed by TGA and vertical combustion test?Flame-retardant properties show that after calcined to 800? in nitrogen and air,the carbon residual rate of the coated fibers were 31.4%and 20.3%,which was three times higher than that of untreated fiber(13.3%and 7.2%),respectively.The coated substrates had self-extinguishing,and reduced the fire hazard.Compared with superhydrophobic coating using the non-etched fiber,the friction resistance and washing resistance of the superhydrophobic surface using etched fiber was significantly improved.When the prepared superhydrophobic coating was used for oil-water separation,the separation efficiency of superhydrophobic fiber can still reach 95%after 20 times of oil-water separation.The flame retardant and superhydrophobic fiber provides the possibility for its treatment and application in harsh environments. |
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